1. Field of the Invention
The present invention relates to a leakage current measurement apparatus for automatically selecting one of non-inductive shunt resistors of 10Ω, 100Ω, and 1000Ω, and measuring leakage currents of an outdoor isolation material for an ultra-high voltage, and more particularly to a leakage current measurement apparatus capable of measuring a relatively wide range of leakage currents with a relatively high precision, even at a remote location, as a measurement range is automatically adjusted within measurement ranges preset by a user when the leakage currents of an outdoor isolation material changes, and being protected against a surge possibly generated by an ultra-high voltage. Also, it can remotely measure, in real-time, leakage currents of an outdoor isolation material installed at a remote location over Ethernet.
2. Description of the Related Art
The measurement range of leakage currents in a currently used isolation material for electrical power distribution is relatively narrow, and also leakage currents are relatively small. Most apparatuses for measuring leakage currents are of a clamp type. Namely, the clamp type leakage current measurement apparatus can measure leakage currents in a specific range of a few to hundreds of μA. However, if leakage currents are out of the range which can be measured by the clamp type leakage current measurement apparatus, then it must be replaced with a new clamp type measurement apparatus. Namely, the new clamp type measurement apparatus has a new clamp with a large or small capacity different from that of the previously installed clamp. Meanwhile, the clamp type leakage current measurement apparatus measures leakage currents as a clamp is hooked in a measured line, and obtains leakage currents in digital or analog format. Also, the clamp type leakage current measurement apparatus must additionally include an external storage device such that it can store measured data at the measurement performing location, or a temporally installable storage device to store specific data therein.
Meanwhile, even though leakage currents generated in an isolation material for electrical power transmission varies in a relatively wide range such as from a few μA to tens of mA, there has not been known a method capable of reliably and safely measuring such a range of leakage currents in real time when ultra-high voltage is being transmitted. Also, to continuously measure the leakage currents using the prior art apparatus, a user must directly operate it on work site at a time point when a measurement range is changed or is expected to change. Also, to analyze data stored in a storage device pre-installed on work site within a predetermined period of time, a user must directly take the data from the storage device.
The prior art leakage current measurement apparatuses may cause damage to a user, when the user accesses the work site to measure leakage currents of isolation material to which an ultra high voltage is applied. Also, since the prior art apparatus does not have any protection device against a surge voltage and current possibly generated as weather conditions changes in a state that an ultra-high voltage is applied to isolation material, its performance is decreased as time goes by and also its life is shortened.